Check the grants on a table

One query lists every role and privilege on a table.

select grantee, privilege_type
from information_schema.role_table_grants
where table_name = 'your_table';

Read the result

You see	It means
No rows for `anon` or `authenticated`	The Data API cannot reach the table for browser requests. Expect 42501.
`anon` with INSERT, UPDATE or DELETE	Signed-out visitors can attempt writes. Only RLS stands in the way.
All three roles with SELECT, INSERT, UPDATE, DELETE	The old automatic defaults. Fine only if RLS is on with sound policies.
Only `service_role`	A private table.

This query matches on table name only. If two schemas hold a table with the same name, add and table_schema = 'public'.

Compare with what you want

Choice	`anon`	`authenticated`	`service_role`	Policies written
Public read	SELECT	SELECT	SELECT, INSERT, UPDATE, DELETE	One: read every row
Owner only	none	SELECT, INSERT, UPDATE, DELETE	SELECT, INSERT, UPDATE, DELETE	Four: own rows only
Private	none	none	SELECT, INSERT, UPDATE, DELETE	None (RLS on, so nothing gets through)

Write the fix for your tables

One table is free. The whole schema with a rollback file is $9 one-time, free during launch.

Paste schema SQL or table names

Waiting for a paste.

Who can reach each table

Your tables show up here, one row each, with a choice of who can reach them.

Start clean: revoke older grants from anon and authenticated first, as the Supabase guide does.

The SQL appears here as soon as a table is found.

Parsed in your browser. Your SQL is never uploaded, and no site or database is scanned.

Questions

Where does Supabase show this without SQL?

The docs mention the Integrations > Data API section of the dashboard for changing table privileges, and the Security Advisor for a list of tables to review.

Sources

Supabase knowledge base: Database API 42501 errors (marked updated 2026-11-03), read 2026-11-10
Supabase docs: Securing your API, read 2026-11-10
Supabase docs: Advisors, read 2026-11-10